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This invention relates to a tool for disintegrating natural and man-made materials such as coal, asphalt, and other useful mineral deposits. It may also be useful in subterranean excavations associated with tunneling and with the placement of subsurface cables, conduits, and pipes. The principles disclosed herein may also have application in the drilling and maintenance of oil, gas, and geothermal wells.
With respect to mining, tools of the class disclosed herein are typically rotationally mounted to a mining excavation machine or a road milling machine. It is desirable that the tool rotates in its attachment so as to avoid non-uniform wear that is likely to reduce the life of the tool in the field.
Generally, the tool is mounted cooperatively with other similar tools on a drum or wheel that also rotates, driving the tools in succession against the natural or man-made formation being worked. Because each tool encounters the formation at an angle, side loading, bending, and rapid accelerations are the stresses experienced by the tools. Furthermore, the materials being worked are often abrasive in nature, or in the case of coal and other less abrasive minerals, are found in abrasive formations that of necessity must be removed in order to extract the target material. High stresses, heat, and abrasion all combine to contribute to the rapid failure of attack tools during use. It is not uncommon for such tools to only last a few hours in actual use, even when the tools are provided with tough carbide inserts and wear surfaces. The dollar cost of individual tools and the down time associated with the replacement of worn out tools are a major expense. It is, therefore, desirable to provide an attack tool having greater durability.
The art is replete with attempts to describe tools that may last longer in use. The investigator is referred to a line of patents culminating in U.S. Pat. No. 6,051,079, incorporated herein by this reference, for a discussion of the prior art and exemplary attempts to overcome the well-documented problems associated with producing a satisfactory tool. Those well versed in the art will acknowledge that the heretofore proposed improvements have not produced a tool that has gained commercial acceptance in the industry, notwithstanding the fact that the proposals have merit in some cases. Therefore, the objective of this disclosure is to advance a tool that overcomes the deficiencies of the prior art and that is suitable for widespread acceptance in the industry.
This invention discloses an attack tool like that for use in the mining and asphalt excavation. The tool features a segmented assembly consisting of a base that is adapted for rotational attachment to mining and excavation equipment, an intermediate wear protector composed of a carbide material that is configured to protect the base from wear during use and to assist in the disintegration of the natural or man-made materials being worked; and a penetrator tip segment, also configured to promote disintegration of the materials being worked. The penetrator consists of a carbide substrate that has a coating of superhard material, such as polycrystalline diamond, cubic boron nitride, or binderless carbide on its working surface. An innovative feature of this invention is that the three segments are bonded along an unmatched, continuously curved interface that enhances attachment and reduces the likelihood of failure due to acceleration and stresses associated with the use of the tool in the field. The interfacial surfaces of the curved interface are not entirely matching in order to accommodate ease of manufacturing and to provide a region where the bonding material may be concentrated. The region of greatest variance is provided at or near the apex, or projected apex, of the curved surfaces, i.e. the region of highest curvature. The apex region is thought to be the least susceptible to bending stresses and accelerations that are likely to promote failure of the bond during use. Additional innovative features will be discussed further in the following detailed discussion of the invention.